The present invention relates to a trim stabilizer device having a foil for speed boats.
The boat position and particular the trim (pitching) of the boat is crucial in terms of cruising performance and fuel economy. Several factors such as load position, speed, the waves and wind in the sea have an effect on trim in motor boats. When the trim of the motor boat increases in relatively fast cruises, mechanical stresses occur on both the hull and the motor as the rear of the boat hull is dragged with high resistance in the sea.
Trim tabs have long been used in speed boats to stabilize the trim. The trim tabs are mounted to the transom of speed boats and they comprise a plate, the bottom surface of which structurally contacts with water, and a mounting part that can be fixed to the transom with which the plate is rotatably communicated by member of a hinge joint. The stabilization of the trim is provided by an actuator (generally a piston) that can make pressure on the tab from the upper side and therefore rotate the tab. It is important how long the trim tabs extend from the bottom end of the boat transom to downwards (towards sea). Thus, as the trim tab is further from the boat to downwards, the counter pressure that the tab stabilizing the boat trim creates is higher, which provides a trim stabilization by pressing the bow of the boat towards the water. However, when trim decreases, as the boat hull will be more in contact with water, the drag and therefore the fuel consumption increase accordingly.
There are many proposals in the art with regard to trim tabs. For instance, U.S. Pat. No. 3,062,167 discloses a trim device which comprises a foil and a concave-formed rod which is communicated with the foil from one side and with trim tabs from the two end sides.
U.S. Pat. No. 2,985,130 discloses a trim tab device that is rotated with the help of a mechanical foil arrangement.
U.S. Pat. No. 3,769,927 discloses trim tabs which can be adjusted independent of each other. The bottom end of an adjustment arm on which a screw is opened is communicated with a bracket on the tab, and as the adjustment arm is rotated, the plate rotates accordingly.
Since the trim tabs of the art are directly communicated with the transom of the boat, water flow along the upper surface of the tab may not be possible. When no trim stabilization is needed, the trim tabs are lifted to transom level or to a higher level (i.e. above the water level); however, this does not contribute to the fuel economy of the boat. The trim tab arrangements according to the art do not allow a height adjustment relative to the boat hull. Furthermore, it may not be possible to tilt trim tabs relative to the transom of the boat. Therefore, cruising performance and comfort are limited in boats equipped with known trim tabs.